SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '336773ad38479d4abb153b435f2a1778c210309ecdc8154f2349eae778aa069e' 
  AND token = 'Ur5Ee9r+ti4sR59/Vspy+5ogxTrAb3rfue9Hbe4A2nQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}